Keywords: Conditions Affecting Unborn Children;Perinatal Assessments;Infertility;Prevention;Estrogens;Androgens;Genetics;Reproductive Assessment by Continuous Breeding (RACB);multigenerational reproductive evaluation;Computer Assisted Semen Analyis (CASA);sperm count and motility;vaginal cytology;estrous cyclicity;endocrine disrupting chemicals;antiretroviral agents;infertility;pregnancy loss;birth defects;dosing pre-weaning mouse pups;rats;mice. A contract was awarded in 2008 which will allow testing of 6-8 environmental agents of interest to the National Toxicology Program, and regulatory agencies such as the Environmental Protection Agency (EPA) and the Food and Drug Administration (FDA), for their ability to impair fertility (conception or pregnancy) and/or fecundity (number of progeny, viable healthy offpring). A Phase 1 study was initiated using a know reproductive/developmental toxicant to evaluate the capability of the contract laboratory to successfully perform all aspects of the multi-generational study design. The study has progressed through production of first- and second-generation offspring, and detailed evaluation of those offspring and analysis of the data is in process.